Flue conduit with internal heat transfer elements



Aug. 31, 1954 o. L. SOCK 2,687,747

FLUE CONDUIT WITH INTERNAL HEAT TRANSFER ELEMENTS Filed May 22, 1951 :a il

`lamented Aug. 31, 1954 FLUE CONDUIT WITH INTERNAL HEAT TRANSFER ELEMENTS Oscar L. Bock, Madison, Wis., assigner to Bock Corporation, Madison, Wis.,

Wisconsin a corporation of Application May 22, 1951, Serial No. 227,547

(Cl. 13S-38) 3 Claims. l

This invention relates to flue baiiles adapted to heat transfer, and more particularly to flue baffles constituting a series `of baiile elements mounted in effective heat transfer relationshiplwithin a metallic flue for accomplishing the efficient transi fer of heat from ilue gases to a surrounding heat absorbing or utilizing medium.

In `heat transfer and heat utilizing apparatus, such, for example, as water heaters suited to domestic and industrial use, it is an element of good design to utilize a metallic tube as a heat conductive flue, and to have that iiue extend in heat transferring relationship through the water or medium to which the heat is to be transferred. With such an arrangement, `the combustion gases are cooled, and the heat therefrom is transferredto the medium which is sought to be heated.

My invention is concerned with the improvement of the eiiciency of the heat transfer from the combustion gases to the heated medium, and

`the consequent reduction of heat losses through heat carried up the chimney by the` combustion gases. In the past, and in similar general arrangements of apparatus, edgewise wound metal baille strips have been placed within metallic ilues to establish a spiral path for the flow of combustion gases, thereby to prolong and lengthen the heat transferring contact of such gases with the metallic ue surface. Such spiral strips were, however, preformed and mounted in a manner allowing for expansion and contraction of the strips, and such that the strips were not in good heat transferring contact with the flues along their lengths. Thus, the benefits of such strips were gained almost entirely from their extensions of the paths of contact of the gases with the nue surfaces.

My invention, on the other hand, has for an ob ject the use of a series of baille elements arranged to extend the time and path of contact between the flue gases and a heat conductive flue, andeach of which baiile elements is heat conductiveand secured in good heat conductive contact to the internal surface of the flue, so that those baffle elements themselves serve to absorb heat from the flue gases and transfer it effectively and efficiently to the medium which is bep ing heated.

As another object, this invention has within its f purview the provision of a metallic flue having a series of baffle elements secured to the internal surface thereof, as described, and wherein the structure and arrangement of the nue and baffle elements are such that the baffle elements 'can l readily be secured to the internal flue surface by spot welding.

In carrying my invention into effect, I have further provided arrangements of baffle elements in a flue which not only affords `an extended path for the passageof flue gases in contact with the flue and bailles, but also effectively increases the heat transmitting flue area from which heat is efficiently transferred from the iiue gases to the medium being heated.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings in which similar characters of reference indicate similar parts throughout the several views.

Referring to the single sheet of drawings:

Fig. 1 is a side sectional view of heat transfer apparatus in the form of a hot water heater embodying a preferred form of my invention; v

Fig. 2 is an end sectional view drawn to a larger scale than Fig. 1 and taken substantially at a position indicated by a line 2-2 in Fig. 1 and in the direction of the arrows;

Fig. 3 is a side sectional view taken substantially on a line 3-3 of Fig. 2;

Fig. 4 is a view similar to Fig.` 2 showing a somewhat modied form of the invention; and

Fig. 5 is a side sectional view taken substantially on a line 5 5 of Fig. Li.

In the exemplary embodiment of my invention which is depicted in the accompanying drawings for illustrative purposes, I have shown its adaptation to heat transfer apparatus in the form of` a water heater, wherein heat from combustion gases is passed through a nue for transfer to water `in a tank. Although it is understood that the concepts and structure of this invention may have other applications, the principles and their struc tural application for the transfer of heat from nue gases to a heat absorbing medium are utilized and illustrated by the structure disclosed.

Consideredl generally and for environmental purposes in connection with the exemplary ap paratus herein shown, the water heater depicted in Fig. 1 `has a generally cylindrical water tank l0, an outer shell i2 of which is capped by a top wall i3 and extends downwardly below a bottom wall I4 to define a combustion chamber U5. The tank IG is preferably covered by heat insulating material I6 which is disposed within an outer metal cover il. The ensemble comprising the heat insulated tank is supported by legs It.

A burner I9 for a suitable and selected fuel is mounted in the combustion chamber if below the bottom wall i4 of the water tank. In the pres# into, and actuated by the temperature of they water in the tank lll.

In addition to heat transferred to the water in the tank through the bottom wall Hl, a metal flue 23 extends through the top and bottom walls I3 and I4 of the tank at a position to be surrounded by the water in the tank and so that the hot combustion or flue gases from the combustion chainber I5 pass therethrough to impart heat to the water. The flue 23, in the present instance, comprises an elongated, open ended and cylindrical metal tube having a relatively thin heat conductive wal-l 24.

It is` practically axiomatic that the efficiency of such apparatus is promoted by effecting the maximum possible heatI transfer from the flue gases to the water or other medium being heated, One manner of accomplishing such heat transfer is to prolong the contact of the flue gases with the heat conductive surface of the flue wall. Another is to provide increased heat absorbing surface in the flue and promoting the effective and efficient transfer of heat from that surface to the mediumbeing heated. My' invention. effectively comprehends both such manners of securing eicient heat transfer.

In the form shown in Figs. l, 2y and 3, metal baille elements are individually secured to the inner surface of the wall 24 of the flue and project inwardly in substantially radial relationship to such Wall. In order to afford effective heat conductivity from the baille elements to the flue wall, each baffle element 2'5 has an integral and angularly formed flange 26 at its outer end which is in heat transferring contact with the flue wall 24 at all times and secured to the wall, as by spot welding, tosupport the baille element and maintain the efliciency of the heat transferring contact.

In order to` provide for good heat conductive contact between the baille elements and nue wall at all times, and so as to insure substantial surface area contact between the flanges 26 of the baille elements and the flue wall Without complicated or expensive forming operations and without the necessity for concern regarding the effects of expansion and contraction of theue and the baffle elements, those flue elements are relatively narrow. For the sake of simplicity, they are generally flat and mounted with their flat baille surfaces substantially normal to the longitudinal axis of the flue. In order to provide substantial surface areas in the baffle elements for the deflection of flue gases and particularly for the absorption of heat from the flue gases, the baffle elements are longer than their width. .In the disclosed structure the baie elements are shorter than the radius of the flue, but their length is greater than twice the width and is such that they extend more than one fourth of the way across the interior of the flue'. These proportions and my disclosed arrangement of parts afford effective operating characteristics, in that they provide for effective and efficient heat transfer without checking the flue to an extent which is' detrimental to combustion, and so as to` cause the production of carbon monoxide gas.

elements follow a spiral pattern in the flue. That is, they are sequentially displaced longitudinally In the form shown in Figs. 1, 2i and 3, the flue i and circumferentially from one another with substantial uniformity of spacing and direction to denne a spiral path. Figs. 2 and 3, when considered together, show the relative positions of baille elements a, b, c, and d circumferentially and axially of the nue. This pattern is continued throughout the length of the iiu'e.

A modified arrangement of the baflle lelements is illustrated in Fig. 4 and 5. The baille elements designated a', bl', c and d indicate the general spiral trend of the .baiile pattern, and also show that sequentially the bailles are staggered relative to one another.

In yboth forms of any baille arrangement and in others that might be devised, the baille elements are in permanent heat conductive relationship to the flue. They absorb heat from the flue gases by contact therewith and effectively and efficiently transfer the heat to the flue and heat absorbing medium. Without unduly obstructing the'ue, they effect limited turbulence of the flue gases and tend toV extend the travel of such gases in their travel through the nue. IThus, they prolong and improve the contact of the flue gases with both the baffle elements and flue, so as to afford more efficient heat transfer to the heat absorbing medium.

While I have illustrated a preferred embodiment of my invention, many rnodications may be made without departing from the spirit of the invention, and I do not wish tov be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States', is:

l. In heat transfer apparatus wherein heat is transferred from combustion gases to a heat absorbing medium surrounding the' exterior of a tubular flue, the ccmbination comprising an elongated and tubular metallic flue of predetermined diameter through which heat from the combustion gases is transferred to the heat absorbing medium in contact with the exterior surface of the nue, and a series vof metallic heat transfer elements of like size and shape welded individually and directly in heat transferring relationship to the internal surface cf the nue in a spiral pattern so that the heat transfer elements present substantial areas and acty effectively to absorb and transmit heat from the combustion gases to the heat absorbing medium without unduly reducing the flue opening fcr the passage of combustion gases, the surfaces of said heat transfer elements each being substantially normal to the longitudinal axis of the flue, said heat transfer elements being shorter than the radius of the flue and having widths -o'f only a small fraction of the flue circumference so that they each occupy less than one-eighth of the area of the flue in a plane laterial to" the longitudinal axis of the flue 4and at their respective levels, and said heat transfer elements also being arranged in av regular se- `quence which embodies substantially uniform axial' and radial spacing of the heat transfer elements within the flue.

2. In heat transfer apparatus as defined in claim l, each of said heat transfer elements cornprising a substantially flat metal strip having a length greater than its width and formed to provide a flange adapted to be spot welded to the i-nnerlue surface with the longitudinal axis of the heat transfer element extending radially into theilue.

3. In heat transfer apparatus wherein heat is transferred from combustion gases to a heat absorbing medium surrounding the exterior of a tubular flue, the combination comprising an elon-` gated and tubular metallic flue through which heat from combustion gases passing therethrough is transferred to a heat absorbing medium in contact with the exterior surface thereof, and a series of metallic heat transfer elements having angularly disposed flanges thereon, which flanges are individually and directly spot Welded to the internal ue surface so that those heat transfer elements extend into the flue and act effectively to absorb and transfer heat from combustion gases Which contact those elements to and through the flue Without unduly reducing the ue opening for the passage of combustion gases, and said heat transfer element forming a series extending longitudinally of the ue with each flue element of the series displaced axially and circumferentially of the flue from the one preceding so that they form a pattern such that the spot welding of the anges to the internal surface of the ue is accomplished sequentially Without having the secured heat transfer elements interfere with the Welding of others.

References Cited in the le of this patent UNITED STATES PATENTS 

